In 1948, the grounds for allowing judicial review of government decisions developed significantly with the Wednesbury case. Since then, this area of review has continued to evolve, with executive decisions increasingly being subjected to rationality or reasonableness assessments.
One of the most important developments in this area was the incorporation of the proportionality test, as part of the protections afforded by the Human Rights Act 1998. The test introduced is relatively straightforward. It requires adjudicators to determine whether the breach or disregard of X fundamental right was proportionate to the need to fulfil Y social/political objective. The test for proportionality comprises a four-stage inquiry[1] aimed at achieving a balance between an official’s goal and respect for the relevant right. Many have argued that the reliance on this test is so extensive that it now acts as a stand-alone ground of review in cases concerned with human rights.2
While the Human Rights Act 1998 is typically associated with proportionality in English courts, often reflecting the importance of the right at stake, a quick survey of the case law suggests that proportionality reasoning has been drawn on by judges in other contexts. This should be welcomed.
Pham Minh Quang
In 2011 the then-Home Secretary Theresa May sought to deprive Pham Minh Quang of his British citizenship. Had the Home Secretary succeeded, Pham would have been rendered stateless. Pham argued that to do so was a violation of his Article 8 right under the ECHR – the right to respect for private and family life, home, and correspondence. When the case reached the Supreme Court, although the appeal was not allowed on Article 8 grounds, the case featured discussion of proportionality.
Drawing on cases concerning important rights such as access to justice, Lord Reed recognised that despite the relevant ECHR context, the European derived test was not explicitly necessary, as proportionality existed as a principle in the common law, though he acknowledged this was “less formally structured” than when under the Human Rights Act. In essence he acknowledged that while such protection could be analysed in the frequently employed test, the principle of proportionality in common law predated the introduction of said test, and remains despite these further developments. In doing so, he proposed that where a case concerned an important right, the court could interfere with any infringement on such rights, subject to implied limitations, and that in practice this approach amounted “in substance to a requirement of proportionality”.3
Lord Reed observed here, as Lord Slynn did in Bank Mellat v Her Majesty’s Treasury (No 2) in 2013, that proportionality varies in its application. It is inherent in the nature of the principle that it cannot be applied in a uniform manner, but rather that it responds to the context in which it’s employed. When considered alongside the recognition of proportionality’s existence in common law, this decision suggests that while the four-pronged test can be used to apply proportionality reasoning, it is not strictly necessary.
Proportionality
An increased reliance on proportionality has led to calls to recognise it as a general ground of review, but others have taken issue with this position. Yossi Nehushtan, for example, strongly rejects this argument, asserting that “proportionality adds almost nothing in terms of the content, the grounds, or the extent of judicial review”. In short, he argues that proportionality should not be recognised as a ground of review because it is, in substance, indistinguishable from a review on the grounds of reasonableness, as both alleged forms of review consist of an exercise of balancing and weighing. However, in considering this argument, the origins of proportionality itself ought to be emphasised.
While I argue that proportionality is a principle which can be extended beyond the human rights context, the fact that proportionality was initially used in this context is not without reason. Proportionality was employed in such instances because the right at stake was of such a fundamental nature that the relevant decision could not be justified on the basis of the rationality or reasonableness of the decision, but rather the need to pass a test of a higher standard. The competing interest had to be directly proportionate to the acknowledged breach of a fundamental right.
On this basis I contend that cases where a proportionality review would be appropriate, outside of the human rights context, are few and far between. However, the judgment in Miller II highlights separate contexts in which such the principle could be applied.
In assessing whether Boris Johnson’s advice to the Queen in 2019 to prorogue Parliament for five weeks was legally valid, the Supreme Court sought to identify where a frustration of parliamentary accountability could be justified. i.e. whether implementing other important constitutional principles justified preventing MPs from exercising their constitutional function in the Commons. In the language used by the courts, they were attempting to ascertain the ‘legal limits’ of these powers, and the extent to which these limits could be challenged by competing interests. While no explicit reference was made in the judgment to the principle of proportionality, we see the Court engage in what was essentially a balancing exercise between two fundamental constitutional principles; attempting to identify the point at which the sacrifice of one becomes disproportionate to upholding or preserving the other.
One might argue that, similarly to Pham, the decision in Miller II is best understood as an exercise of the common law proportionality principle, a constitutional principle with a wide scope, but one which is judicially understood and foregoes the need to adhere to the Human Rights Act’s four-stage test.
A hypothetical
Consider the following hypothetical case: the existence of Act X prevents the retention of a particular type of data which can be analysed to trace an organisation’s hardware. This applies to both private bodies and international actors. The effect of the legislation is such that when UK government systems and critical infrastructure systems come under an unexpected attack, the attack cannot be prevented, disrupted or traced. Given that Parliament is in recess and key communication systems have been corrupted, the government feels compelled to take immediate action. While recalling Parliament is possible, the government decides that given the speed of the cyber attacks, it is necessary in this situation to repeal Act X immediately in respect of government bodies in order to gain the necessary information to defend against any further action by the attackers. While a fundamental constitutional principle has been breached, and the executive has overstepped its authority regarding primary legislation, the government believes such action is both necessary and in the public interest. The government’s action becomes subject to judicial review.
This case could be reasoned along the lines of Miller II: that in order to justify the breach of a constitutional principle in favour of a competing interest, the legal limits of the principle must be ascertained, whatever they may be.
Or, we could call the court’s task what it is. A balancing exercise. An exercise of proportionality. In our hypothetical case, as in the Miller case, the court must decide whether the given action by the government was proportionate when confronted with the relevant threat to the public interest. The judges in Miller II may have stopped short of explicitly referencing the proportionality principle; doubtless, they were worried about the risk of extending the principle beyond its typical rights-based context. But, that doesn’t change the reality that, in substance, this is precisely what occurred. When courts are forced to balance an infringement of a constitutional principle with defending another, then we should understand this as an exercise in gauging proportionality.
As acknowledged by Yossi Nehushtan and other critics of the case for proportionality as a general ground of review, the reasoning in both Miller II and as we saw in our proposed hypothetical scenario could be analysed under a number of existing grounds: reasonableness, legitimate expectations, even procedural impropriety. Yet, the logic behind any such judgement is fundamentally best articulated using the language of proportionality.
It might be argued that it is pedantic to suggest that we use proportionality where these other judicial review grounds could be invoked, given that both lines of reasoning will typically produce a similar outcome, and indeed more cases might be better assessed under other judicial review grounds. However, legal clarity is important. Acknowledging the reality of developments in case law is important. When properly examined, the case law does not suggest that proportionality can be confined to the classical mould of a ground of review, but rather that it is of a flexible, overarching nature in the manner of a constitutional principle. Had more judges adopted a line of reasoning akin to that of Lord Reed and Lord Slynn, that perhaps general principles were more appropriate than any one applicable ground of review, progress might have been made towards addressing the current grey area surrounding proportionality. If so, we might have usefully built on the foundation of common law proportionality provided by Pham.
Charlotte O’Brien.
Charlotte O’Brien completed an internship with the Constitution Society in 2025. She is a final year law student at Queen’s College, University of Cambridge.
The Constitution Society is committed to the promotion of informed debate and is politically impartial. Any views expressed in this article are the personal views of the author and not those of The Constitution Society.
[1] The test involves inquiring into whether a restriction on a fundamental right (1) pursues a legitimate objective; (2) is rationally connected to that objective; (3) is necessary to achieve the objective; and (4) strikes a fair balance between the right and the public interest.
2 See Paul Craig, Jeffery Jowell and Lord Justice Laws
3 Pham (Appellant) v Secretary of State for the Home Department (Respondent) UKSC/2015/0150